This Week in Political Science: Divisive Primary Edition

The “Niggerhead” incident and related mudslinging among the GOP presidential candidates prompts the question: how competitive is too competitive when it comes to primaries? Political scientists have long studied what is called the divisive primary hypothesis, and John wrote a post back in early 2008 (see also the comments) that presented some relevant research. John suggested that divisive primaries had little effect on the nominee’s performance in the general election:

The logic is this: a divisive primary is more likely to arise if an incumbent is unpopular or presiding over a weak economy, simply because this incumbent will attract more challengers. Leaving the economy and presidential popularity out of the equation risks overestimating the effects of divisiveness.

The 2008 election afforded a fresh opportunity to examine this question, especially because of the lengthy battle between Barack Obama and Hillary Clinton. Several studies of 2008 suggest that the Democratic primary contest had little impact on Obama’s general election performance.

Using a survey that tracked individual voters from the primary to the general election, Michael Henderson, D. Sunshine Hillygus, and Trevor Thompson (gated, ungated) examine whether and why Clinton supporters did or did not support Obama in the general election. They find that 71% of Clinton supporters ended up voting for Obama. Moreover, supporters of Clinton and the other Democratic candidates were no more likely to stay home on Election Day. The most important factors that predicted a vote for McCain among supporters of the other Democratic candidates were not frustration with the primary election’s outcome but ideology and political issues, especially the Iraq War. The authors conclude:

Our analysis offers individual-level results that call into question the longstanding assumption that thwarted voters will necessarily stay home or defect to the opposing-party candidate because of hard feelings from a divisive nomination phase.

In a 2010 paper, Amber Wichowsky and Sarah E. Niebler (gated) argue that then Senator Obama was actually helped by the primary’s competitiveness. Wichowsky and Niebler seek to disentangle competitiveness (the closeness of the election) from divisiveness (the negativity of the campaign) and then estimate their respective effects on Obama’s general election performance. The authors find that more competitive primaries featured more political ads, but a smaller proportion of negative ads. Competitiveness did not breed divisiveness. Moreover, the more competitive the state’s primary or caucus, the better Obama did in that state in the general election:

After controlling for Democratic performance in the previous presidential election, a one percentage point increase in the relative competitiveness of the Democratic contest over the Republican contest leads to three tenths of a percentage point increase in Democratic vote share, a relatively small effect, but opposite that suggested by earlier research.

For one, Obama was an unknown candidate with an issue position on Iraq that was popular among Democrats and many Independents. Second, he was able to flex his substantial organizational and financial muscle throughout the primary season. Indeed, the protracted nomination may have helped Obama increase his donor and volunteer base…Moreover, absent geographic, demographic, and ideological factions, such as those characterizing the contests of 1968, 1976, and 1980, a more unified Democratic party may have been in a better position to reap the benefits of a vigorously contested nomination.

In general, political commentators still exhibit more concern about the effect of divisive primaries than the evidence warrants.